The specific aim of this study is to determine in a randomized double-blind placebo-controlled trial the effect of hormonal replacement with conjugated estrogens and progestins on disease activity in postmenopausal women with systemic lupus erythematosus (SLE). Since the research hypothesis is that estrogen replacement therapy (HRT) does not increase the frequency of flares, the study has been designed to be able to detect minimal increases in the risk of flare in patients taking HRT. Over a 3-year period, postmenopausal women with SLE will be enrolled and randomized to receive continuous conjugated estrogens plus 5mg medroxy-progesterone acetate for 12 days per month or placebo for a followup of 12 months.